A printed wiring board having an electric circuit that involves hard switching at an inverter, a switching power supply or the like is equipped with a noise filter for suppressing electromagnetic noise. In a noise filter for suppressing common mode noise, for example, a common mode choke coil serving as an inductor in a common mode is mounted on a printed wiring board similarly to filter circuit elements such as a bypass capacitor.
Japanese Utility Model Laying-Open No. 5-006820 (PTD 1) describes a board-type noise filter having a common mode choke coil mounted on an insulating stand with four corner legs, where the insulating stand is mounted on a wiring board. Filter circuit elements such as a capacitor except for the common mode choke coil, and external connection terminals are directly mounted on the wiring board.
In a noise filter for suppressing normal mode noise, a normal mode choke coil serving as an inductor in a normal mode is mounted on a printed wiring board similarly to filter circuit elements such as a bypass capacitor.